top dead center sensor

never heard of one. Is it anything like a can of squelch, muffler fluid, that sort?

Per workerboy:

Could that be the same as the crank sensor that my '98 has?

Tells the 'puter where the crank is rotation-wise at any given moment.

good point. CPS, I know of. Just never heard it called a TDC Sensor, though of course that's what it'll tell you.

Nope- best of my knowledge, there wasn't one in 89

Is thew timing adjusted by rotating the distributor? Then shouldn't as crank position is detected by the distributor.